1. Field of the Invention
This invention relates to a camera system of the kind having a motor-driven diaphragm disposed within an interchangeable lens.
2. Description of the Related Art
The 35 mm camera of a type using a non-interchangeable lens is generally called a compact camera. The camera of that type has a so-called lens-shutter device which is arranged to serve both as a shutter and a diaphragm. In addition to that, it is a general tendency to have the camera of that type arranged to automatically wind and rewind a film by using a power source disposed within the camera. The camera of another type called a single-lens reflex camera which uses an interchangeable lens is also provided with a power source arranged within the camera for operating various devices including an automatic exposure device, an automatic film winding device, an automatic focusing device and an automatic film rewinding device. However, since the power source voltage is limited, the power source must be efficiently used by time serially carrying out the complex processes of these devices.
Cameras of the kind using a motor for preparatory processes such as film feeding, shutter charging and for driving the diaphragm have recently been proposed. One example of them has been disclosed in Japanese Patent Application Laid-Open No. SHO 49-95621. In the case of cameras of this kind, an automatic film winding process begins during the process of fully opening the diaphragm aperture by the above stated automatic exposure device. The simultaneous performance of the diaphragm driving and film feed driving actions results in an excessively large consumption of electrical energy. This has been apt to cause a failure or a faulty action of the electrical circuits of the camera. In addition as the power source voltage drops at low temperature, the above stated problem becomes more serious under a low temperature condition.
A camera of the kind performing a mirror driving action and a diaphragm driving action by means of motors separately provided for these purposes has recently been proposed (Japanese Patent Application Laid-Open No. SHO 49-95621). However, that arrangement is not suited for a camera as it necessitates an increase in the capacity of the power source. In addition to that problem, the camera of that type tends to malfunction when the power source voltage drops under a low temperature condition.
A camera which is arranged to prevent overlapping of rush currents by somewhat staggering the driving start time of the film winding motor and that of the shutter charging motor after completion of an exposure is disclosed in U.S. Pat. No. 4,659,201. The advantage of this arrangement is furthered by the present invention, whereby a problem resulting from simultaneous or overlapped driving actions of a motor disposed within a camera body and another motor disposed within an interchangeable lens used as an accessory is solved by virtue of an arrangement for communication between the interchangeable lens and the camera body.
Further, cameras of the kind using a stepper motor which is of a simple structure and permits the manufacture of a control circuit at a reduced cost have recently been proposed. In the conventional camera of this kind, the rotator of the stepper motor is formed with a permanent magnet. However, while the diaphragm aperture of the camera is designed to be normally in a full aperture position, the aperture has often been accidentally stopped down by some impacts or vibrations.
To solve this problem, there has been proposed a technique for bringing the diaphragm back into its full aperture position by allowing the stepper motor to rotate in the direction of opening the aperture in case that the diaphragm is not in the full aperture position at the beginning of a photometric action before a shutter release action, as disclosed, for example, in Japanese Patent Application Laid-Open No. SHO 58-111022. This proposed improvement, however, has presented the following problem: In cases where the diaphragm aperture has been accidentally stopped down by vibrations of the camera or the like, the full aperture is not obtainable unless a photometric switch is actuated. Therefore, when the photographer looks into the view finder of the camera, it might be too dark for a focusing operation because of the stopped down aperture. Further, even if the focusing operation could be accomplished, the depth of field is deep under that condition as the aperture is stopped down. Therefore, a picture which is then actually taken by pushing the shutter release button with the stopped-down aperture adjusted closer to a full aperture position would be out of focus. Further, the arrangement to bring the diaphragm back into its full aperture position by operating a photometric switch requires an additional length of time, which prevents seizing a shutter chance.